In PTL 1, a remote distance in an approximately orthogonal direction from a positioning point to a line center is calculated based on accurate positioning data of the positioning point using an RTK technique and route data from a route database. Thus, it is determined whether the positioning point is present in a location of an area other than a railway track area, in a location of an area within a track, or a caution area or a dangerous area within the location of the track, and accurate information on safety and locations are provided to individual workers present in the railway tracks.